1. Field of the Invention
The present invention relates to radiation-resistant steels used for manufacturing vessels of water-cooled power reactors, and may be utilized for other installations whose construction material is exposed to neutron radiation during the course of operation.
The invention is readily adapted for application in the manufacture of vessels for high-power water-cooled reactors.
2. Description of the Prior Art
The prior art teaches steels formerly used in the production of atomic reactors, or those specifically developed for pressure vessels such as boiler shells, steam-generator drums, etc., which show resistance to radiation when exposed thereto under operating conditions. However, it has been revealed in the course of prolonged operation that with the exposure dose effecting said steels being in excess of 2.0.10.sup.19 N/cm.sup.2 (exposure temperature being 290.degree. C.), the material of reactor vessels becomes prone to embrittlement. This, in turn, substantially reduces the impact strength of said material and increases the fracture transition temperature thereof. As a result, the operating reliability and durability of atomic reactors are greatly impaired.
There is also known in the art a steel employed for similar purposes, having the following composition, in percent by weight: carbon, from 0.06 to 0.15; manganese, 0.15 to 0.4, silicon, 0.16 to 1; nickel, 2.5 to 8; molybdenum, 0.25 to 1.25; chromium, 0.5 to 0.9 phosphorus, of up to 0.015, sulfur, of up to 0.015, aluminum, of up to 0.08; nitrogen, of up to 0.006; oxygen, of up to 0.004; iron, the balance.
However, the aforesaid steel is only applicable when the exposure dose does not exceed 4.10.sup..multidot. N/cm.sup.2 (E.gtoreq.0.5 MeV).
Featuring the highest characteristics is a steel of the following composition, in percent by weight:
______________________________________ carbon from 0.13 to 0.18 manganese from 0.3 to 0.6 silicon from 0.15 to 0.3 nickel from 1.0 to 1.6 chromium from 1.6 to 2.5 molybdenum from 0.5 to 0.7 vanadium from 0.01 to 0.12 cerium from 0.002 to 0.04 copper from 0.01 to 0.1 antimony from 0.0005 to 0.009 tin from 0.0005 to 0.009 phosphorus from 0.002 to 0.01 sulfur from 0.001 to 0.01 iron, the balance ______________________________________
Contained in said steel as an admixture, is arsenic in an amount of 0.004 to 0.02 percent by weight. The steel of the above-mentioned composition can be used with the exposure dose being 1.10.sup.20 N/cm.sup.3 (E.gtoreq.0.5 MeV), at a temperature of 300.degree. to 350.degree. C.
The disadvantage of the steel referred to above is its susceptability to embrittlement when exposed to radiation.